New Melones Dam - Specifications

Specifications

New Melones Dam and its reservoir comprise the independent New Melones Unit of the Central Valley Project. The dam's primary purpose is to control the runoff from 904 sq mi (2,340 km2), or about 92 percent, of the watershed of the Stanislaus River, a major tributary of the San Joaquin River. At 625 ft (191 m) high from the foundations and 1,560 ft (480 m) long, and containing 15,700,000 cu yd (12,000,000 m3) of material, New Melones is the second largest embankment dam in California, after Oroville. With a crest elevation of 1,135 ft (346 m), the dam rises for 594 ft (181 m) above the streambed. Flood waters are released through an unlined spillway about a mile (1.6 km) northwest of the dam, with a capacity of 112,600 cu ft/s (3,190 m3/s). The dam also has a set of outlet works, which can release up to 8,300 cu ft/s (240 m3/s).

The impounded water behind the dam forms New Melones Lake, which at full pool of 1,088 ft (332 m) above sea level encompasses 12,500 acres (5,100 ha) of surface water and a volume of 2,400,000 acre·ft (3,000,000 dam³). About 450,000 acre·ft (560,000 dam³), 19 percent of the reservoir's capacity, is reserved for flood control. During flooding events, the dam is operated to keep flows on the Stanislaus River below 8,000 cu ft/s (230 m3/s), although this figure may be lowered depending on flow conditions in the San Joaquin River. From 1979 to 1993, the dam and reservoir prevented an estimated $128,500,000 in flood damage.

New Melones Dam also serves for water supply and electricity generation. The dam's hydroelectric power plant is located at its base on the north side of the river, and has a rated hydraulic head of 480 ft (150 m). The plant houses two 150.0 MW Francis turbines for a total capacity of 300 MW. Releases are made on a peaking basis and are also dictated by irrigation and flood control requirements below the dam. The plant produces about 323 million kilowatt hours annually. By controlling the flows of the Stanislaus River, the dam and reservoir also make available 200,000 to 280,000 acre·ft (250,000 to 350,000 dam³) of surplus water each year. Under contract, the dam furnishes an annual 150,000 acre·ft (190,000 dam³) to the Stockton East Water District and Central San Joaquin Water Conservation District. The increase in water supply from New Melones Dam has "translated into prosperity for the region, allowing the growth of cities including Tracy and Manteca, and irrigating high-value crops including almonds, walnuts and grapes."